Kate Thomas

IQ and non-clinical psychotic symptoms in 12-year-olds: results from the ALSPAC birth cohort

Background Non-clinical psychotic symptoms appear common in children, but it is possible that a proportion of reported symptoms result from misinterpretation. There is a well-established association between pre-morbid low IQ score and schizophrenia. Psychosis-like symptoms in children may also be a risk factor for psychotic disorder but their relationship with IQ is unclear. Aims To investigate the prevalence, nature and frequency of psychosis-like symptoms in 12-year-old children and study their relationship with IQ. Method Longitudinal study using the Avon Longitudinal Study of Parents and Children (ALSPAC) birth cohort. A total of 6455 children completed screening questions for 12 psychotic symptoms followed by a semi-structured clinical assessment. IQ was assessed at 8 years of age using the Wechsler Intelligence Scale for Children (3rd UK edition). Results The 6-month period prevalence for one or more symptoms was 13.7% (95% CI 12.8–14.5). After adjustment for confounding variables, there was a non-linear association between IQ score and psychosis-like symptoms, such that only those with below average IQ score had an increased risk of reporting such symptoms. Conclusions Non-clinical psychotic symptoms occur in a significant proportion of 12-year-olds. Symptoms are associated with low IQ and also less strongly with a high IQ score. The pattern of association with IQ differs from that observed in schizophrenia.

Investigating whether adverse prenatal and perinatal events are associated with non-clinical psychotic symptoms at age 12 years in the ALSPAC birth cohort

BACKGROUND Non-clinical psychosis-like symptoms (PLIKS) occur in about 15% of the population. It is not clear whether adverse events during early development alter the risk of developing PLIKS. We aimed to examine whether maternal infection, diabetes or pre-eclampsia during pregnancy, gestational age, perinatal cardiopulmonary resuscitation or 5-min Apgar score were associated with development of psychotic symptoms during early adolescence. METHOD A longitudinal study of 6356 12-year-old adolescents who completed a semi-structured interview for psychotic symptoms in the Avon Longitudinal Study of Parents and Children (ALSPAC) birth cohort. Prenatal and perinatal data were obtained from obstetric records and maternal questionnaires completed during pregnancy. RESULTS The presence of definite psychotic symptoms was associated with maternal infection during pregnancy [adjusted odds ratio (OR) 1.44, 95% confidence interval (CI) 1.11-1.86, p=0.006], maternal diabetes (adjusted OR 3.43, 95% CI 1.14-10.36, p=0.029), need for resuscitation (adjusted OR 1.50, 95% CI 0.97-2.31, p=0.065) and 5-min Apgar score (adjusted OR per unit decrease 1.30, 95% CI 1.12-1.50, p<0.001). None of these associations were mediated by childhood IQ score. Most associations persisted, but were less strong, when including suspected symptoms as part of the outcome. There was no association between PLIKS and gestational age or pre-eclampsia. CONCLUSIONS Adverse events during early development may lead to an increased risk of developing PLIKS. Although the status of PLIKS in relation to clinical disorders such as schizophrenia is not clear, the similarity between these results and findings reported for schizophrenia indicates that future studies of PLIKS may help us to understand how psychotic experiences and clinical disorders develop throughout the life-course.

Maternal tobacco, cannabis and alcohol use during pregnancy and risk of adolescent psychotic symptoms in offspring

BACKGROUND Adverse effects of maternal substance use during pregnancy on fetal development may increase risk of psychopathology. AIMS To examine whether maternal use of tobacco, cannabis or alcohol during pregnancy increases risk of offspring psychotic symptoms. METHOD A longitudinal study of 6356 adolescents, age 12, who completed a semi-structured interview for psychotic symptoms in the Avon Longitudinal Study of Parents and Children (ALSPAC) birth cohort. RESULTS Frequency of maternal tobacco use during pregnancy was associated with increased risk of suspected or definite psychotic symptoms (adjusted odds ratio 1.20, 95% CI 1.05-1.37, P = 0.007). Maternal alcohol use showed a non-linear association with psychotic symptoms, with this effect almost exclusively in the offspring of women drinking >21 units weekly. Maternal cannabis use was not associated with psychotic symptoms. Results for paternal smoking during pregnancy and maternal smoking post-pregnancy lend some support for a causal effect of tobacco exposure in utero on development of psychotic experiences. CONCLUSIONS These findings indicate that risk factors for development of non-clinical psychotic experiences may operate during early development. Future studies of how in utero exposure to tobacco affects cerebral development and function may lead to increased understanding of the pathogenesis of psychotic phenomena.

Investigating if psychosis-like symptoms (PLIKS) are associated with family history of schizophrenia or paternal age in the ALSPAC birth cohort

Psychosis-like symptoms (PLIKS) occur in about 15% of the population, but it is unclear to what extent PLIKS share aetiological mechanisms in common with those for schizophrenia. We examined whether the presence of PLIKS was associated with a family history of schizophrenia (FH-SCZ), or with advancing paternal age, using data from 6356 children in the ALSPAC birth cohort who participated in a semi-structured PLIKS interview at 12 years of age. We found no evidence of association between FH-SCZ and suspected or definite PLIKS (adjusted OR=0.94, 95%CI 0.44, 2.00; p=0.880). There was weak evidence that advancing paternal age was associated with increased PLIKS (adjusted OR per 10-year age increase=1.23, 95%CI 0.99, 1.55; p=0.058). Although not a priori hypotheses, family history of depression (adjusted OR=1.28, 95%CI 1.04, 1.57; p=0.018), and younger maternal age (adjusted OR per 10-year age increase=0.62, 95% CI 0.47, 0.82; p<0.001) both showed stronger evidence of association with suspected or definite PLIKS. Overall our findings provide little evidence that these established risk factors for schizophrenia show a similar relationship with PLIKS, suggesting that the presence of PLIKS is unlikely to be a strong marker of early expression of the pathology underlying schizophrenia. Whether future studies of PLIKS will increase our understanding of mechanisms underlying the development of schizophrenia, or prove useful in prediction of this disorder, remains to be seen.

Association between locus of control in childhood and psychotic symptoms in early adolescence : results from a large birth cohort

Introduction. Specific attributional styles have been demonstrated in individuals with psychotic disorders and are implicated in the development of psychotic symptoms. We aimed to examine the association between locus of control (LOC) assessed in childhood and psychotic symptoms reported in early adolescence. Methods. We used a prospective longitudinal design using data from a large birth cohort (the Avon Longitudinal Study of Parents and Children, ALPSAC). 6455 subjects completed a semistructured clinical interview assessing 12 individual psychotic symptoms at a mean age of 12.9 years. A measure of LOC was previously collected in the cohort at the age of 8. Results. Children who reported an externalised LOC at age 8 were at increased risk of reporting both broadly defined (OR 1.77, 95% CI 1.49 to 2.08) and narrowly defined (OR 2.06, 95% CI 1.58 to 2.67) psychotic symptoms at age 13 years. These associations were only slightly attenuated after adjustment for potential confounders. The associations were similar for broadly defined specific paranoid symptoms but weaker for narrowly defined specific paranoid symptoms. Conclusions. An externalised LOC appears to be associated with later reporting of psychotic symptoms in early adolescence. Further investigation of the role of attributional styles, such as LOC, in increasing the risk for psychotic disorders, is warranted.

Association of measures of fetal and childhood growth with non-clinical psychotic symptoms in 12-year-olds: the ALSPAC cohort

Background Previous studies have suggested that impaired fetal and childhood growth are associated with an increased risk of schizophrenia, but the association of pre-adult growth with non-clinical psychotic symptoms (psychosis-like symptoms) in children is not known. Aims To explore the associations of body size at birth and age 7.5 years with childhood psychosis-like symptoms. Method Prospective cohort of children followed up from birth to age 12: the ALSPAC cohort. Results Data on 6000 singleton infants born after 37 weeks of gestation. A one standard deviation increase in birth weight was associated with an 18% reduction in the risk of definite psychosis-like symptoms after adjusting for age and gestation (Odds ratio (OR) = 0.82, 95% CI = 0.73–0.92, P = 0.001). This association was partly confounded by maternal anthropometry, smoking during pregnancy, socioeconomic status and IQ. A similar association was seen for birth length and psychosis-like symptoms, which disappeared after controlling for birth weight. There was little evidence for an association of 7-year height or adiposity with psychosis-like symptoms. Conclusions Measures of impaired fetal, but not childhood, growth are associated with an increased risk of psychosis-like symptoms in 12-year-olds.

Childhood facial emotion recognition and psychosis-like symptoms in a nonclinical population at 12 years of age: Results from the ALSPAC birth cohort

Introduction. Nonclinical psychotic symptoms (for example, low intensity or low frequency psychotic symptoms such as ideas of reference or single word auditory hallucinations) are common in adolescents and may be associated with an increased risk of developing a psychotic disorder in adulthood. Those at high risk of developing a psychotic disorder appear to perform poorly on facial emotion recognition tasks but the relationship between facial emotion recognition and nonclinical “psychosis like symptoms” (PLIKS) in children is unclear. We aimed to examine the association between childhood facial emotion recognition and PLIKS in adolescents. Methods. Longitudinal study using a large birth cohort. 6455 subjects completed a semistructured clinical assessment for psychotic symptoms (the PLIKSi) at the mean age of 12.9 (SD=0.23). Facial emotion recognition (using the DANVA) was previously assessed at the age of 8 in the cohort. Results. There was no increase in odds of reporting any PLIKS either in relation to the total score on the measure of facial emotion recognition or for the individual emotion scores of fear, sadness, anger, and happiness. Similar results were also found when examining more intense and/or more frequently experienced psychotic symptoms. Conclusions. Deficits in facial emotion recognition in 8-year-olds do not appear to predict later reporting of nonclinical psychotic symptoms in early adolescence. The results do not support the proposal that recognition of emotion is a trait phenomenon in those individuals at increased risk for psychosis. However, further research is warranted in older children/adolescents when more subtle emotion recognition deficits can be investigated.

Interleukin-18 Polymorphism and Physical Functioning in Older People: A Replication Study and Meta-Analysis

BACKGROUND Levels of the proinflammatory cytokine interleukin-18 (IL-18) are raised in old age and are associated with reduced physical functioning. Previous studies have indicated that the C allele of the rs5744256 polymorphism in the IL-18 gene is strongly associated with reduced circulating IL-18 levels. This variant has previously been associated with improved locomotor performance in old age, but the finding requires independent replication. METHODS We examined the association between the IL-18 polymorphism rs5744256 and physical functioning in three cohorts with a total of 4,107 participants aged 60-85 years: the English Longitudinal Study of Ageing, Caerphilly, and Boyd Orr. We meta-analyzed (N = 6,141) the results with data from the original paper reporting this association: Iowa-Established Populations for Epidemiological Study of the Elderly and InCHIANTI cohorts. Physical functioning was assessed by timed walks or the get up and go test. As locomotor performance tests differed between the cohorts and the distributions of times to complete the test (in seconds) were positively skewed, we used the reciprocal transformation and computed study-specific z scores. RESULTS Based on the three new studies, the estimated linear regression coefficient per C allele was 0.011 (95% confidence interval [95% CI]: -0.04 to 0.06). A meta-analysis that pooled the data from all studies showed weak evidence of an effect, with a regression coefficient of 0.047 (95% CI: 0.010 to 0.083). CONCLUSIONS We did not replicate an association between the IL-18 rs5744256 polymorphism and the physical function in people aged 60-85 years. However, pooling data from all studies suggested a weak association of the C allele of the rs5744256 single nucleotide polymorphism on improving walking times in old age.